title: Thin film voltammetry of wild type and mutant reaction center proteins from photosynthetic bacteria.
abstract: Photosynthetic reaction centers (RC) convert light into electrical potential via a series of electron transfers between protein-bound, redox-active cofactors. Direct voltammetry was used to characterize the RC protein from Rhodobacter sphaeroides and mutants with focus on the primary electron donor (P) cofactor. Cyclic voltammetry (CV) and square wave voltammetry (SWV) of lipid and polyion films of RCs revealed similar chemically irreversible processes, and starting, switching, or preconditioning potential of -0.15 V was required to observe a well-defined P/P(+) oxidation peak at ∼0.95 V versus normal hydrogen electrode. An irreversible chemical reaction following voltammetric oxidation led to peak decreases upon multiple scans. Mutant RCs with site-directed amino acid modifications in the vicinity of P displayed shifts of oxidation peak potential correlated with those reported from redox titrations. These studies illustrate the utility of thin film voltammetry in characterizing redox properties of bound cofactors in RC proteins.
authors.affiliation: Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA.
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Amy M
authors.initials: AM
authors.lastname: LaFountain
authors.forename: Nikki
authors.initials: N
authors.lastname: Magdaong
authors.forename: Marcel
authors.initials: M
authors.lastname: Fuciman
authors.forename: James P
authors.initials: JP
authors.lastname: Allen
authors.forename: Harry A
authors.initials: HA
authors.lastname: Frank
authors.forename: James F
authors.initials: JF
authors.lastname: Rusling
mesh_terms: D002244:Carbon / Q000737:chemistry; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D006108:Graphite / Q000737:chemistry; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D015203:Reproducibility of Results; D012242:Rhodobacter sphaeroides / Q000201:enzymology*
chemical_list: D050505:Mutant Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; C009139:pyrolytic carbon; D002244:Carbon; D006108:Graphite; D004134:Dimyristoylphosphatidylcholine